ZURICH (Reuters) - A small number of patients with the hardest-to-treat form of hepatitis B were effectively cured after taking Roche Holding AG's Pegasys drug, according to results of a late-stage clinical trial released on Friday.

The 537-patient trial, whose initial results were reported in October, showed that Pegasys beat standard therapy against the difficult-to-treat form of hepatitis B.

Twelve people taking Pegasys alone or in combination with standard therapy lamivudine, but none on lamivudine alone, achieved the most complete response to treatment that is possible, Roche said in a statement.

"Although the numbers are low, clinically this is a very significant result, as it is indicative of complete remission," it added.

The phase III trial presented at a medical congress in Germany showed Pegasys was more effective than lamivudine in treating patients with "variant" hepatitis B and that adding lamivudine to Pegasys did not make it work any better.

Lamivudine is the generic name of Epivir made by GlaxoSmithKline Plc. Roche plans to file this year for regulatory approval of Pegasys in hepatitis B.

The trial found 43% of those treated with Pegasys alone had viral loads decline to the target level, while only 29% of those on lamivudine did.